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Smith Mini Plane Rebuild

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Old 03-21-2009, 08:01 PM
  #1
Trasky
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Default Smith Mini Plane Rebuild

I was flying my Sig Smith Mini Plane the other weekend. I've only flown the plane maybe 8 times. I'm somewhat a beginner and in fact during this flight I was learning how to use both the ailerons and rudder in conjuction while making a turn. The plane was flying fine until I went into a right turn and the plane did not come out as it did not respond any more. The battery was dead! I thought I had charged the battery enough but apparently not. The plane stayed in the air for a few secons while it tightly turned but eventually spiraled down into a tree.

The fuselage split in two with the back half completely disengrating. The tail pieces were intact but were stuck in a tree. The receiver attena that I looped around the rudder was what got caught in the branch and kept the tail and servos/receiver hanging. Both wings broke in half with the right half of the top wing completely crushed. I never found the battery which is funny to me.

Since half of the top wing and most of the N-strut assembly was toast I thought it may be easier just to rebuild a monoplane. From research I found that the second wing of a biplane only lifts 20% extra because of the interference both wings cause on each other. To provide extra lift I made the bottom wing 6 inches longer. Along with the increased wing span and reduction of weight without the top wing and struts, the plane should be able to fly like it used to.

My only concern is how stable the plane will be as it is now a bottom winged plane. The plane will probably have a greater tendency to roll over. If someone that has flown a bottom wing plane could comment that would be great.
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Old 03-21-2009, 09:01 PM
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sir crashallot
 
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Default RE: Smith Mini Plane Rebuild

i had a wayfarer biplane cant remember the manufacturer and was built by my friend, however after about a year of flying it i had a missahap and was flying inverted across the strip,
DEADSTICK at 8 maybee 10 ft off the ground i had no option but to land it inverted as it would have stalled if id have tried to flip it right side up. shatterd the top foam venered wing and broke one of the ply main caben struts clean off the fus,
the next weekend it was back at the field with the other cabane sawn clean off and some little patches of red covering to cover the bare ply of what remained of the cabane strut, after carefull ballancing and an ugly long nose it flew, wasnt as forgiving on the landings as it had to come in fast due to the high weight to wing area ratio. but from the looks of yours you may get away with it
keep the engine as far back on the mount as possible so it fetches the prop closer to the wing too, heck its all fun and if it flys again its a bonus just remember to make sure the repairs are strong enough to handel the forces
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Old 03-21-2009, 11:27 PM
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RC MANIAC119
 
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Default RE: Smith Mini Plane Rebuild

This beast will fly just fine. Just make sure your CG is on the thickest part of that bottom wing, and you have a lot of aileron throw.

GO FLY!!
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Old 04-26-2009, 07:08 AM
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Trasky
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Default RE: Smith Mini Plane Rebuild

The plane flies well with the single wing. Landings seem to even be easier as the plane has less tendency to flip onto its back without the top wing.

One problem I have is that the engine seems to be overheating inside the cowl. I think my inlet area is too great compared to much outlet area so there isn't a proper pressure difference. Would blocking off the inlet opposite the engine help?
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Old 04-26-2009, 07:33 AM
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Default RE: Smith Mini Plane Rebuild

Yes, blocking off the opposite side will help, but to get the most cooling you can, open the bottom rear to 1-1/2 the opening size of the one infornt of the engine. Air is just like any other fluid, it does not like to take the hardest path through the cylinder fins, it would rather go right past the fins and out the bottom. So baffle the inside infront of the engine, force the air to go to the cylinder head, you'll be amazed on how effective a small piece of lite ply extending from the centerline of the engine bearers to the nose of the cowl will be.
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Old 04-26-2009, 09:47 AM
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Default RE: Smith Mini Plane Rebuild

Putting a baffle in the cowl sounds like a good idea. I took my cowl off and I saw discoloration of the cylinder head in the back and side near the top of the cowl so the engine was overheating. I hope no significant damage was done as I did three flights with the cowl on.

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Old 04-26-2009, 09:59 AM
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Default RE: Smith Mini Plane Rebuild

If the engine still runs at temp, your fine, but the baffle will be vertical, running along the crank centerline, on either side of it, just up to the cylinder head. The air doesn't need to be forced tightly around the cylinder like a briggs and stratton engine, but get it flowing to the cylinder area is important. I did the same in my cowl of the smith, helped in keeping the needle settting more consistant by stabilizing the engine temp's.
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Old 04-26-2009, 10:07 AM
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Default RE: Smith Mini Plane Rebuild

Would having a horizontal baffle running under the left inlet to the cylinder be beneficial to prevent the air from just going under the motor toward the bottom of the cowl?
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Old 04-26-2009, 11:36 AM
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Default RE: Smith Mini Plane Rebuild

No, it would be a good thing, but just find a way to direct the air to the cylinder and out the cowl cheek or the bottom rear. I had a pitts muffler and a magnum 46 in mine, the baffle went vertical to the cylinder, cutting the cowl in half inside, most of the air went out the cheek, but some made it out the bottom. This is something you must do if you ever go to gas engines, it sounds like alot of work, but the fact that the engine will run more reliable because of the baffle is worth the piece of mind. After installing the baffle, I never deadsticked due to the engine overheating and leaning out.
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Old 05-01-2009, 12:50 AM
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Default RE: Smith Mini Plane Rebuild

Planebuilder66-

AMAZING Mini!!!!!!!!!!!!!!!

I like it.
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Old 05-01-2009, 03:45 PM
  #11
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Default RE: Smith Mini Plane Rebuild

I loved it, but as usual, I sold it to fund other projects, someone here on RCU ended up with it, don't know who, but they must love the little sucker. I'm going through a phase right now where I'm building kits again and scratching again. The arf is still a viable option for me, that is in the fact that it get's me in the air fast when I just want to fly. But I've been buying planes that I use to have a long time ago, the mini will be bought and built again, right now I recently bought a BUSA smoothie and another GP extra kit and a few other ones I use to have years ago, from sailplanes to power, I got about 9 and still counting. But I did total my pulse due to me being an idiot, so I bought a super skybolt ARF, it'll keep me flying for a while. That is if I can avoid flying into soccer goal posts![:@] Thanks for the kind words on the mini, just wish I knew who bought it, like to know it's fate.
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Old 05-01-2009, 07:36 PM
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Default RE: Smith Mini Plane Rebuild

I miss mine. I put it into an unrecoverable spin. This little bipe sure drew a lot of attention.
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Old 01-09-2010, 12:05 AM
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Default RE: Smith Mini Plane Rebuild

Hi,

Don't want to hi-jack anything, but here is my Smith Miniplane built from Harold Osborne Plans and powered by a 52cc Gas. 88 inch Wingspan. Yes, it's had a few encounters with mother earth, still going strong, fun to fly, gentle as a SIG LT-40, gets all the attention at the field. [img][/img]
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